Lubricants are used primarily to reduce friction and wear on parts which move in contact with each other. Also, lubricant compositions serve to transfer heat from moving parts. Lubricants are compounded from stable component materials to maximize the useful life of the lubricant. The component materials include representative basestocks such as petroleum, synthetic esters, hydrocarbon-based polymers, silicone fluids, polyglycols, polyphenyl ethers, phosphate esters, and alkyl benzenes as well as other fluids known in the art. A wide number of additives are also employed, such as antioxidants, viscosity improvers, corrosion inhibitors, antiwear agents, and the like. However, under high temperature operating conditions, the lubricant, comprised of a basestock and one or more additives, tends to break down by any one of several degradative mechanisms, such as oxidation, polymerization or the like. As a result, the working surfaces, typically metal, which come in contact with the lubricant composition tend to become coated with carbonaceous deposits. In time, these deposits form a smooth varnish-like coating which adheres tenaciously to the working surfaces, necessitating solvent treatment in an effort to remove the varnish. Alternatively, the deposits appear as a velvet-like coating which is less tenacious but still requires scraping or solvent treatment for removal.
Deposits of these types occur on working surfaces in a variety of applications where lubricant compositions are employed. One such application is chain lubrication. Chain lubricants are used to protect chains and bearings in ovens, furnaces and kilns. The lubricant compositions are usually applied by brush, spray, drip operation, wheel, or bath immersion. During operation, the lubricant is carried along on a belt or chain which moves from a low temperature area to a higher temperature area and back. Thus, the lubricant is continuously cycled through one of a range of temperatures over a range of cycling periods. Chain lubricants are employed in machinery used in various high temperature operations, such as plywood drying, glass forming, paint curing, lithography, annealing, tempering, and baking.
As the maximum operating temperature for the oven, furnace or kiln increases, and as the period of exposure to high temperature increases, the degradation rate of the chain lubricant composition accelerates. Likewise, the formation of carbonaceous deposits on the working surfaces also accelerates. The deposits add to the weight of the chain, impair the flexibility of the chain, and increase the power draw on the drive motor. The deposit is typically inspected visually and deposits are removed where possible by scraping, brushing, or solvent action. When the deposit builds up to an unacceptable extent and cannot be removed, the chain is discarded.
Deposit formation occurs in all lubrication environments where the operating conditions are sufficient to promote breakdown of the lubricant composition components. The problem of carbonaceous deposit formation exists in a variety of other applications requiring lubricants, such as in crankcase lubrication, turbine lubrication, compressor lubrication, gear lubrication, bearing lubrication, and the like.